[PATCH] Fix multiple minor tzset glitches [BZ #24004]

[Paul Eggert]

On 3/13/19 7:52 AM, Florian Weimer wrote:
> On the other hand, for files which we do not poll for changes (such as
> /etc/resolv.conf previously, and /etc/gai.conf and /etc/nsswitch.conf
> presently), we regularly receive requests to add such polling.

Yes, and it would be good to add a way to control polling of /etc files,
and whatever method is used to control polling of /etc/nsswitch.conf
etc. could also be used to control polling of /etc/localtime. Still, the
current situation with /etc/localtime is not good: it disagrees with the
documentation and with common practice elsewhere. So I suggest that we
fix it and also look into adding an API to control polling.

One API might be something like a new include file etcpoll.h with an API
like this:

  etcpoll (ETC_NSSWITCH_CONF, ETCPOLL_NOW);
  etcpoll (ETC_GAI_CONF, ETCPOLL_ALWAYS);
  etcpoll (ETC_LOCALTIME, ETCPOLL_DISABLE);

where NOW means reconsult the file now, ALWAYS means always reconsult
the file before every use of its data, and DISABLE means stop
reconsulting. That sort of thing.